Dude that sucks big time. Grid search is the best option. I have lost watches and glasses in the sea and found them the next day. And when my trex 250 exploded in long grass i found all but one of the parts by replaying the video i took and following the path of the debris until all was found..
So for future events using a keychain cam even if you're not going to publish the video, can be used to find down helis.
I used the aerial search technic with my 600 and a gopro to find a guys glider in some trees.
Good luck mate. You will find it with patience and systematic grid patterns.